Spatial epidemiology of carbapenem-resistant Enterobacteriaceae (CRE) in Tennessee, 2015-2018 Open Access

Winston, Kyle (Spring 2021)

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Carbapenem-resistant Enterobacteriaceae (CRE) is an emerging public health threat. Bacteria in this group are difficult to treat and readily share resistance genes. Because CRE was traditionally viewed as a hospital-acquired infection, most studies have investigated risk factors and transmission dynamics associated with healthcare settings. However, community spread of CRE is also an important and understudied threat. Beef cattle production is a potential driver of community transmission. Cattle have been shown to carry CRE organisms and cattle farms regularly spread bacteria into the surrounding environment. Analyses presented here examine the spatial structure of beef cattle farming, CRE rates, and covariates at the county level in Tennessee from 2015 to 2018. CRE case counts were collected by the Tennessee Department of Health through its mandatory disease reporting surveillance system. These counts, and yearly populations, were pooled at the county level across the four-year study period, and rates per 100,000 person-years were calculated for each county. Three potential exposures were evaluated—the number of beef cattle operations with 1-49 heads of cattle in each county, the number of beef cattle operations with 50 or more heads of cattle in each county, and the beef cattle counts in each county. Variable mapping, Moran’s I spatial autocorrelation tests, aspatial linear regression, and spatial Durbin regression were conducted to determine the association between beef cattle and CRE rates at the county level. These analyses demonstrated a weak but statistically significant protective effect between beef cattle and CRE rates, as well as a strong spatial autocorrelation in CRE rates between neighboring counties. These ecological findings provide insight into the utility of using spatial regression methods to understand community transmission of diseases and demonstrate there is community transmission of CRE demonstrate inter-county community spread of CRE.

Table of Contents

Introduction 1

Methods 9

Results 14

Discussion 25

References 28

Appendix 32

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